SEEG is a safe and accurate procedure for the invasive assessment of the epileptogenic zone. Traditional Talairach methodology, implemented by multimodal planning and robot-assisted surgery, allows direct electrical recording from superficial and deep-seated brain structures, providing essential information in the most complex cases of drug-resistant epilepsy.

aBBreViatiONS EEG = electroencephalography; EZ = epileptogenic zone; FCD = focal cortical dysplasia; MTLE = mesial temporal lobe epilepsy; RF-TC = radiofrequency thermocoagulation; SEEG = stereoelectroencephalography. SuBmitted August 28, 2014. accepted December 8, 2014. iNclude wheN citiNg Published online June 19, 2015; DOI: 10.3171/2014.12.JNS141968. diSclOSure Dr. Cardinale is a consultant for Renishaw Mayfield SA, the manufacturer of Neuromate, and a former consultant for Medtronic, the manufacturer of the O-arm device. The other authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. OBJect Radiofrequency thermocoagulation (RF-TC) of presumed epileptogenic lesions and/or structures has gained new popularity as a treatment option for drug-resistant focal epilepsy, mainly in patients with mesial temporal lobe epilepsy. The role of this minimally invasive procedure in more complex cases of drug-resistant epilepsy, which may require intracranial electroencephalographic evaluation, has not been fully assessed. This retrospective study reports on a case series of patients with particularly complex focal epilepsy who underwent stereoelectroencephalography (SEEG) evaluation with stereotactically implanted multicontact intracerebral electrodes for the detailed identification of the epileptogenic zone (EZ) and who received RF-TC in their supposed EZ (according to SEEG findings). methOdS Eighty-nine patients (49 male and 40 female; age range 2-49 years) who underwent SEEG evaluation and subsequent RF-TC of the presumed EZ at the authors' institution between January 2008 and December 2013 were selected. Brain MRI revealed structural abnormalities in 43 cases and no lesions in 46 cases. After SEEG, 67 patients were judged suitable for resective surgery (Group 1), whereas surgery was excluded for 22 patients (Group 2). Thermocoagulation was performed in each of these patients by using the previously implanted multicontact recording electrodes and delivering RF-generated currents to adjacent electrode contacts. reSultS The mean number of TC sites per patient was 10.6 ± 7.2 (range 1-33). Sustained seizure freedom occurred after TC in 16 patients (18.0%) (13 in Group 1 and 3 in Group 2). A sustained worthwhile improvement was reported by 9 additional patients (10.1%) (3 in Group 1 and 6 in Group 2). As a whole, 25 patients (28.1%) exhibited a persistent significant improvement in their seizures. More favorable results were observed in patients with nodular heterotopy (p = 0.0001389), those with a lesion found on MRI (not significant), and those with hippocampal sclerosis (not significant). Other variables significantly correlated to seizure freedom were the patient's age (p = 0.02885) and number of intralesional TC sites (p = 0.0271). The patients in Group 1 who did not benefit at all (21 patients) or who experienced only a transient benefit (30 patients) from TC underwent microsurgical resection of their EZ. Thermocoagulation was followed by se...

Object The authors report on the use of stereoelectroencephalography (stereo-EEG) in the presurgical electroclinical evaluation of infants and very young children with focal drug-resistant epilepsy. Methods Fifteen patients (9 girls and 6 boys, mean age 34.1 ± 7.3 months, range 21–45 months), potentially candidates to receive surgical treatment for their focal drug-resistant epilepsy, were evaluated using stereo-EEG recording for a detailed definition of the epileptogenic zone. Stereoelectroencephalography was indicated because neuroradiological (brain MRI) and video-EEG data failed to adequately localize the epileptogenic zone. Stereotactic placement of multicontact intracerebral electrodes was preceded by the acquisition of all pertinent anatomical information from structural and functional MRI and from brain angiography, enabling the accurate targeting of desired structures through avascular trajectories. Stereoelectroencephalography monitoring attempted to record habitual seizures; electrical stimulations were performed to induce seizures and for the functional mapping of eloquent areas. Stereoelectroencephalography-guided microsurgery, when indicated, pointed to removal of the epileptogenic zone and seizure control. Results Brain MRI revealed an anatomical lesion in 13 patients (lobar in 2 cases, multilobar or hemispheric in 11 cases) and was unremarkable in 2 patients. One patient underwent 2 stereo-EEG studies. The arrangement of the intracerebral electrodes was unilateral in all but 1 case. One patient died the day following electrode placement due to massive brain edema and profound hyponatremia of undetermined cause. In 8 cases intracerebral electrical stimulations allowed mapping of functionally critical areas; in 3 other cases that received purposeful placement of electrodes in presumably eloquent areas, no functional response was obtained. Of the 14 patients who completed stereo-EEG monitoring, 1 was excluded from surgery for multifocality of seizures and 13 underwent operations. Postoperatively, 2 patients exhibited an anticipated, permanent motor deficit, 3 experienced a transient motor deficit, and 2 experienced transient worsening of a preexisting motor deficit. Three patients developed a permanent homonymous hemianopia after posterior resections. Histological analysis revealed cortical malformations in 10 cases. Of the 10 patients with a postoperative follow-up of at least 12 months, 6 (60%) were seizure-free (Engel Class Ia), 2 (20%) experienced a significant reduction of seizures (Engel Class II), and 2 (20%) were unchanged (Engel Class IV). Conclusions The present study indicates that stereo-EEG plays a prominent role in the presurgical evaluation of focal epilepsies also in the first years of life and that it may offer a surgical option in particularly complex cases that would have scarcely benefitted from further medical treatment. Results of stereo-EEG–guided resective surgery were excellent, with 80% of patients exhibiting a substantial improvement in seizures. In consideration of the potentially life-threatening risks of major intracranial surgery in this specific age group, the authors recommend reserving stereo-EEG evaluations for infants with realistic chances of benefiting from surgery.

SEEG-guided RF-THC proved to be a safe and effective option in our small case-series of NH-related focal epilepsy. The indications to this treatment were strictly dependent on findings of intracerebral recording by SEEG, which can define the role of the NH in the generation of the ictal discharge.

SUMMARYPurpose: To analyze the topography of the epileptogenic zone (EZ) and the etiologic substrate as risk factors for sleep-related focal epilepsy. Methods: Three hundred three patients (172 males and 131 females, mean age at surgery 25.6 ± 13.1 years), who were seizure-free after resective surgery for drug-resistant focal epilepsy, were retrospectively reviewed. Statistical analysis was conducted to evaluate the risk of presenting sleep-related epilepsy (SRE) against topography of resection (assumed to correspond or to include the EZ) and results of histology. Results: Thirty-nine patients (12.8% %) presented with an SRE. At bivariate analysis, a higher frequency of SRE was associated with a frontal lobe EZ (p = 1.94 · 10 )9 ) and Taylor's FCD (TFCD, p = 2.20 · 10 )16 ), whereas architectural FCD (p = 0.00977), ganglioglioma (p = 0.02508), and mesial temporal sclerosis (p = 2.47 · 10 )5) were correlated with a reduced frequency of SRE. Multivariate analysis demonstrated that the only variable significantly associated with SRE was the presence of a TFCD, which increased 14-fold the risk of SRE [p = 1.66 · 10 )10 ; risk ratio (RR) = 14.44]. Discussion: In this study, we have demonstrated a significant and strong association between SRE and TFCD in a select population of patients with drug-resistant focal epilepsy submitted to surgical resection of the EZ. Although our results cannot be applied to the entire spectrum of SRE, the presence of TFCD as the underlying etiology should be considered when evaluating patients with SRE, because surgery can provide excellent results on seizures in these cases.